Nickel Chrome Alloy as Resistance Material and Heating Element

The nickel-chromium system shows that chromium is quite soluble in nickel. This is a maximum at 47% at the eutectic temperature and drops off to about 30% at room temperature. A range of commercial alloys is based on this solid solution. Such alloys have excellent resistance to high temperature oxidation and corrosion and good wear resistance. They are suitable for making high-value electrical resistors, heating wires, heating cords and cables.

NiCr 8020 is suitable for heating elements used for temperatures upto 1200°C. This is used for electrical cooking equipment, precison resistors. Oxidized wires of these alloys display better insulation properties.

NiCr 6015 is suitable for heating elements used for temperatures upto 1150°C. This is used for electrically heated equipment, high resistance and potientiometer resistors.

NiCr 3020 is suitable for heating elements used for temperatures upto 1050°C. Inspite of relatively high Fe content, these alloys are resistant to oxidation and chemical corrosion. They are used for making heating elements of cooking equipment, heating cords and cables.

A marked increase in electrical resistivity is observed with increasing chromium additions. An addition level of 20% chromium is considered the optimum for electrical resistance wires suitable for heating elements. This composition combines good electrical properties with good strength and ductility, making it suitable for wire drawing. Commercial grades include Nickel-chromium alloy and NiCr alloy. Small modifications of to this composition may be made to optimise it for particular applications.